Interesting thoughts. Would like to chuck another scenario into the mix.
Vehicle crossing . he doesn't have to call vacated as there is no requirement to ( which I completely disagree with but hey perhaps being at Heathrow for 24 years has made have these thoughts)
So vehicle is crossing. ATC controller distracted. When he turns round he sees no vehicle. he has an aircraft on approach. He tries to call the vehicle but by then he is parked up radio off having a brew.
would you as the controller give that aircraft clearance to land ??
If so why when you cannot confirm where that vehicle is and you have had no positive call back from the vehicle saying he/she has vacated.
If you did give it clearance and there was an incident what would you say ?
" I didn't see it guv" and take Arsen wengers normal stance on things?
I don't think that would wash when up before the beak !!!
An RT message is after all recorded and does not have any ambiguity